With the packet data service being more and more widely applied, how to charge the packet data service accurately and reasonably has become a general concern to which the operators are paying more and more attention.
In the current General Packet Radio Service (GPRS) charging system, service data flow of the terminal can be recognized only at the level of Access Point Name (APN) and Packet Data Protocol Context (PDP Context), so the charging has to be performed according to the APN and the PDP Context. However, in practical application, multiple parallel service data flows will probably be carried through the same PDP Context, and different services may need different charging manners. The current GPRS charging system cannot satisfy this requirement. For instance, when the terminal has both flow media service and multimedia message service at the same time and these two services are borne in the same APN and PDP Context, but different charging rules are applied to charge these two services, say flow media service needs to be charged according to the terminal's data flow or service duration, while multimedia message service needs to be charged according to the events like sending or receiving a multimedia message. In order to utilize the same charging scheme upon different types of packet data services, it is needed to put forward a new charging manner for the current GPRS charging system and introduce a general flow based charging mechanism.
Considering the above situation, the 3rd Generation Partnership Project (3GPP) is discussing how to implement the IP-based data Flow Based Charging (FBC) currently. As to just one packet data service, the consumed data flow when the terminal is utilizing this service is called Service Data Flow (SDF) that can be the aggregation of multiple IP data flows. Multiple different packet data services can be borne in one APN and PDP Context. In this way, the charging fineness based on IP flow is much higher than that based on one PDP Context, and the IP-based FBC can truly reflect the resource occupied status of a certain service data flow. Therefore, IP-based FBC can provide more abundant charging means for the operators or service providers.
The system configuration, function requirements and information interworking procedure of the FBC are all described in 3GPP. FIG. 1A shows the FBC system configuration for the online charging, in which a Customized Application for Mobile Network Enhanced Logic (CAMEL) based Service Control Point (SCP) 101 and a Service Data Flow Based Credit Control Function (CC) 102 constitute an Online Charging System (OCS) 106. CC 102 is connected through the Ry interface with a Service Data Flow Based Charging Rule Function (CRF) 103, CRF 103 is connected through the Rx interface with an Application Function (AF) 104 and through the Gx interface with a Traffic Plane Function (TPF) 105; CC 102 is connected through the Gy interface with TPF 105.
FIG. 1B shows the FBC system configuration for the offline charging. A CRF 103 is connected through the Rx interface with an AF 104 and through the Gx interface with a TPF 105, TPF 105 is connected through the Gz interface with a Charging Gateway Function (CGF) 107 and with a Charging Collection Function (CCF) 108, respectively.
According to the definition of the FBC function entities in 3GPP, the function of each function entity will be described hereinafter.
TPF 105 is a function for bearing packet data flow and can differentiate packet data packages that belong to different packet data service flows. TPF 105 is used for collecting offline charging information and executing online credit control. When the bearer of packet data flow is changed, for example, in the case of bearer establishment, bearer modification, bearer deletion or other procedures, TPF 105 will request CRF 103 through the Gx interface for the charging rules and the charging rules request message may carry the terminal-related information, the bearer characteristic, network-related information and etc. The terminal-related information may be the Mobile Station International Integrated Services Digital Network (ISDN) Number (MSISDN), the International Mobile Subscriber Identifier (IMSI) and etc, the bearer characteristic related information may be the Quality of Service (QoS) parameter, the network-related information may be the Mobile Network Code (MNC), the Mobile Country Code (MCC) and etc. TPF 105 performs packet data filtering and charging information collecting upon the corresponding packet data flow according to the charging rules returned by CRF 103. A TPF 105 may be provided with services by one or more CRF 103. When there are multiple CRF 103 providing services for a same TPF 105, a corresponding CRF 103 may be selected according to the terminal's identifier to interact with this TPF 105. TPF 105 supports the predefined charging rules and the predefined packet data flow filter.
CRF 103 is a function for storing the charging rules which supports both dynamic and static charging rules. Dynamic charging rules are generated in real time according to the charging strategy of the packet data service and applied to the corresponding packet data flow, while static charging rules are invariable through the utilized course of the packet data service by the terminal and may be activated dynamically by some events during the utilized course of the packet data service by the terminal. CRF 103 may select proper charging rules according to the information provided by TPF 105, AF 104 or OCS 106. When TPF 105 requests CRF 103 for the charging rules or when a specific event occurs, CRF 103 will provide the selected charging rule for TPF 105. One CRF 103 may correspond to multiple TPF 105.
AF 104 represents all application-related functions. AF 104 may be a network entity of an operator or that of a third part service provider. AF 104 provides the corresponding information for CRF 103, so that CRF 103 can select or configure corresponding charging rules according to this information. The information provided by AF 104 for CRF 103 includes: identifier information of the packet data flow, information for selecting the charging rules, application/service identifier, triggered events for the application/service charging rules, type of the packet data flow, rate of the packet data flow and etc. The identifier information of the packet data flow may be wildcarded; the type of the packet data flow may be video, audio and etc. Either the type of the packet data flow or the rate of the packet data flow is the optional parameter. One AF 104 may correspond to multiple CRF 103. When there are multiple CRF 103 corresponding to a same AF 104, the corresponding CRF 103 can be selected according to the terminal identifier to interact with AF 104.
CC 102 is a function for executing credit control, which is applied only to online charging system and may be implemented by adding new functions to the existing OCS 106. CC 102 in OCS 106 may provide relevant information for selecting the charging rules to CRF 103 through the Ry interface.
CGF 107/CCF 108 is a function applied to offline charging system and may be implemented by following the existing means in GPRS charging system.
If the bearer network is a GPRS network, TPF 105 is a Gateway GPRS Support Node (GGSN) and AF 104 is a service gateway or service server in the Packet Data Network (PDN). When the IP Multimedia Subsystem (IMS) is borne in the GPRS network, AF 104 is a Proxy Call Session Control Function (P-CSCF) and CRF 103 is a newly added logic entity.
As described above, the charging configuration and the functions implemented by the function entities may also be applied to 3GPP2 network frameworks.
In the existing charging methods based on the FBC mechanism, the TPF selects the serving CRF according to the terminal identifier and the AF addresses the serving CRF according to the terminal identifier as well. As the TPF is a function belonging to the bearer layer while the AF is a function belonging to the application layer, and a terminal may have different identifiers in different layers, the above-described terminal identifier at the AF and that at the TPF may be the same or different. By means of network layout and configuration, it is guaranteed that the same CRF can be addressed according to a same terminal's different identifiers in different layers.
According to the existing addressing means based on the FBC mechanism, only when the TPF, the CRF and the AF are located in a same Public Land Mobile Network (PLMN) can the TPF and the AF address the same CRF in terms of a same terminal, thus implement the correct CRF addressing. If the terminal utilizes a TPF located in a PLMN other than the terminal's home PLMN, it is still a pending problem in the FBC mechanism as how to make the TPF address the correct CRF according to the terminal identifier, obtain the required charging rules and thus implement packet data flow based charging. In addition, when the AF and the CRF are located in different PLMN, the AF is unable to address the CRF serving the corresponding terminal currently according to the terminal identifier by means of the existing addressing method.